It is well known to restrain an occupant in a seat by an automatically deployed shoulder belt extending diagonally across the upper torso and a lap belt extending across the lower torso.
U.S. Pat. No. 3,770,294, issued to Hammer, and assigned to the assignee of this invention, discloses a shoulder belt having the outboard end fixedly mounted on the vehicle roof adjacent the rear corner of the door and a lap belt having the outboard end mounted on the door by a retractor. The inboard ends of the lap and shoulder belts are joined to the outboard end of a control belt whose inboard end is mounted on the vehicle body inboard the seat by a control belt retractor having a winding effort greater than the lap belt retractor so that the juncture of the lap, shoulder and control belts is drawn inboard to establish the lap and shoulder belts in their respective restraining position about the occupant. The shoulder belt extends slidably through a carriage movable fore and aft along the roof rail above the door. The carriage has a normal rearward position adjacent the fixedly mounted end of the shoulder belt to establish the shoulder belt in the diagonal restraining position across the upper torso. When the door is opened, the shoulder belt carriage is moved forwardly to stow a substantial length of the shoulder belt along the roof rail above the door so that the inboard ends of the shoulder belt and lap belt are moved substantially upwardly and forwardly away from the seat as permitted by unwinding of the control belt from the control belt retractor. Simultaneously, the outward swinging movement of the door moves the outboard end of the lap belt outward and forward as permitted by unwinding of lap belt from the door mounted lap belt retractor.
It would be desirable for the shoulder belt of the Hammer type belt system to be mounted on the vehicle body by a retractor so that the length of the shoulder belt could be adjusted independently of movement of the lap belt and control belt to precisely fit the size of a particular occupant and facilitate forward leaning movement of the occupant within the seat. However, the forward movement of the belt carriage would tend to unwind shoulder belt from the shoulder belt retractor instead of unwinding control belt from the control belt retractor as required to obtain the desired substantial upward and forward movement of the inboard ends of the lap and shoulder belt.